1. Field of the Invention
The present invention relates to a power-line communication device configured to perform power-line communications, so as to control an electronic apparatus by using a power line connecting a direct-current (DC) power supply configured to supply power for the electronic apparatus and a control circuit.
2. Description of the Related Art
Hitherto, where a copier system includes units that require no high-speed data transfer, serial communication has been used for transferring data and controlling the units. The above-described technology is disclosed, for example, in Japanese Patent Laid-Open No. 11-284606. According to the above-described serial communication, signals transmitted and/or received include a signal indicating that the serial communication is started, a communication clock, transmission data, a latch signal, and so forth so that data can be transmitted with increased reliability.
FIG. 7 schematically shows the known serial communication. Communication is performed between a unit 701 on the control side and a unit 702 to be controlled. Power lines 703 denote five different signal lines including a line S-CS* used for transmitting a signal S-CS indicating that the serial communication has started, a line S-CLK used for transmitting a communication clock S-CLK, a line S-TXDATA used for transmitting transmission data S-TXDATA from the unit 701 to the unit 702, a line S-RXDATA used for transmitting reception data S-RXDATA from the unit 702 to the unit 701, a line S-LC* used for transmitting a data-latch signal S-LC* used for latching the transmission data S-TXDATA.
The number of units of the copier system increases as the functions of the copier system increase. Although data is transmitted by serial communication, the units need to be connected to one another by using communication lines used for transmitting a transmission signal and/or a control signal, which increases the number of signal lines. More specifically, since a single unit requires at least five lines including the communication lines and the control lines, the number of communication lines used for controlling and/or operating the units is obtained by multiplying the number of units by five. Thus, the total number of communication lines increases as the number of units (functions) increases.
As described above, the use of serial communication has become inadequate for reducing the number of signal lines. Namely, it is difficult to ensure space for providing all of the above-described signal lines therein in confined spaces of a cabinet of the copier system. Further, all of communication lines required for transmitting transmission data and control signals must be ensured without reducing the functions of the copier system.
Data communication may be performed by using a cable that is not primarily developed, as a communication line, for example, a power-line cable that is used for supplying power and that is connected between a power supply and a control circuit. In that case, however, a signal may not be correctly transmitted due to noise generated at the time where a switching element of the switching power supply is turned on and/or off.